1. Field of the Invention
The present invention relates to an optical semiconductor device used as a transmitting or receiving optical module in an optical communication system.
2. Related Background Art
As a transmitting optical module of this type, a light-emitting element such as a semiconductor laser (LD) or a light-emitting diode (LED) for converting an electrical signal into a light signal and sending the light signal onto an optical fiber and a drive integrated circuit (IC) for driving the light-emitting element are mounted on a single insulating substrate as a hybrid IC, and this substrate is housed in a package. Similarly, as a receiving optical module, a hybrid IC substrate mounting a light-receiving element such as a photodiode (PD) or phototransistor for converting a light signal received from an optical fiber into an electrical signal and an amplifying IC for amplifying the output signal from the light-receiving element is housed in a package.
Each package has a structure having a through hole into which the optical fiber is inserted, and terminal pins used for an electrical input/output operation. The packages are classified into two types according to alignment state of the terminal pins. One of them is, as shown in FIG. 7, a DIP (Dual In-line Package) type in which terminal pins 72 extend from a bottom surface of a package 71 to be substantially perpendicular to the major surface of a hybrid IC substrate 73. The other one is, as shown in FIG. 8, a butterfly type in which terminal pins 82 extend from side surfaces of a package 81 to be substantially parallel to the major surface of a hybrid IC substrate 83. Note that reference numerals 76 and 84 in FIGS. 7 and 8 denote optical fiber insertion ports, respectively.
In the above structure, the hybrid IC substrate 73 or 83 mounting the optical semiconductor device and the IC is assembled inside the alignment of the terminal pins 72 or 82. More specifically, the hybrid IC substrate 73 or 83 is fixed on a substrate base 74 mounted on the bottom surface of the package, and the terminal pins 72 or 82 are aligned to surround the substrate assembly.
For this reason, the package size is increased both in the DIP type and the butterfly type in which the terminal pins extend laterally.
Electrical connections between the hybrid IC substrate 73 or 83 and the terminal pins 72 or 82 are performed through wires 75 or the like. Since a distance between the substrate and each terminal is large, an inductance is increased, and as a result, electrical characteristics are impaired.
Furthermore, since the hybrid IC substrate 73 or 83 is fixed in the package 71 or 81 quite independently of the terminal pin group, it is difficult to align the substrate with the terminal pins.